When 50- something Caroline Lieberman takes her young male friend on one of their many fabulous vacations, it’s always in style. Couple’s massages at the

airport. Helicopters to Monaco. Stays at the Four Seasons and the Peninsula hotels in romantic cities around the world. Sure, they have decades between them and little in common, but no matter: “He’s a marvelous companion,” she says.

Lieberman’s travel partner isn’t a 20-something playboy. He’s a 4-year-old, 15-pound Havanese named Mumbai. He and Lieberman, who works in the arts, have spent the past three summers in Europe — Monaco, Milan and Venice — and are hoping to pull off a late summer trip to Italy soon.

Just as the most fabulous New Yorkers are enjoying summer travels most of us can only admire from our cubicles, so, too, are their lucky dogs. Michael Brigante, the manager of American Kennels on the UES, has seen hundreds of his well-heeled clients jetset with their pets.

“They travel to every continent —North Africa, the Middle East, pretty hard-core traveling — some by private plane,” he says.

Lieberman and Mumbai typically fly commercial, but in first or business class — of course — so there’s plenty of room for the two of them. Little Mumbai doesn’t require his own seat because he travels in a carrier doggy bag. And the transatlantic trip is well worth it for the fluffy white pup.

“Traveling with a dog in Europe is wonderful — most establishments welcome them. Europe made him realize he has the right to sit on a chair or bench,” Lieberman says.

Not all city pets will be lucky enough to take a first-class international jaunt before the summer ends, but for those embarking on less-

far-flung travels, here are some tips:

* Prep your pup Noted dog trainer Brian Kilcommons says owners should start working with their pets long before departure. “Whether they’re [traveling] in a carrier or a crate, get the dog used to it well in advance,” he says, “so they know it’s a safe place.”

* Talk to your vet Dr. Carolyn Clarke of VERG South, a veterinary clinic in Brooklyn, says, “Animals of certain ages, breeds or with a specific illness may not do well in flight.” She doesn’t recommend medicating dogs either, but says that if yours is flying in the cabin, as opposed to cargo, “light sedation, such as an antihistamine, may provide a mild calming effect.”

* Pack wisely Bring your own dog food. “A lot of dogs don’t do well with diet changes,” says Brigante. “No one wants to treat their dog for diarrhea in Monaco.” The same goes for less exotic locales, like the Jersey Shore.

* do your paperwork For international travel, “make sure all of your documentation is done 100 percent so your dog isn’t quarantined, or forced to go back to the US,” Brigante says. Wherever you’re headed, says Clarke, “keep a copy of all medical records on your person.”